The present invention relates to a method of and apparatus for regenerating an adsorption agent. More particularly this invention concerns the step of reactivating carbon or charcoal that has adsorbed impurities in waste water or the like.
After an adsorption agent such as activated-carbon particles has been used it is necessary to strip the adsorbed materials off the particles in a regeneration or deadsorption process. This is usually effected by contacting the particles with a hot gas that vaporizes and carries off the material adsorbed onto them.
In the commonest method the adsorption agent is loaded into one side or end of a multistage or rotating furnace. The particles flow from one side or end to the other of this furnace continuously. The rate of flow, which determines the treatment time, is calculated so that by the time the particles have reached the downstreamor outlet end of the arrangement they have been fully regenerated. In such an arrangement it is frequently necessary to use a very long residence time in the device, often up to several hours, and the particles are frequently abraded together to such an extent that they are effectively milled down to a smaller average particle size.
It has been suggested to use fluidized-bed reactor for the regeneration of active coal used in the purification of drinking water. In German Pat. No. 951,864 for instance, it has been suggested to provide a multistage fluidized-bed reactor. At least three superposed beds are provided which are interconnected via vertical feed tubes so that the particles flow from one side of one bed to the other, then drop down to the next bed and flow in the opposite direction to the end of that bed, then down to the next bed, and so on. Such a reactor is normally a very large structure and once again the particles are usually subjected to excessive abrasion inside the arrangement. Furthermore it is necessary to treat a large quantity of the adsorption particles at one time in order to completely fill the reactor and obtain uniform results.
In another known system (German Pat. No. 971,417) it has been suggested to feed the particles into one end of a horizontally elongated fluidized bed. A plurality of walls formed with or forming restrictions subdivide this bed into a plurality of compartments so as to slow down the flow rate from one end to the other of the particles. Such an arrangement does indeed reduce the abrasion of the particles and the overall size of the apparatus, however overactivation of the particles is a frequent occurrence and losses in the arrangement are in the region of 10% of the activated carbon fed in.